Knowing whether someone you love has a problem with alcohol or drugs isn't as straightforward as it sounds. Despite the stereotypes of the staggering drunk or the emaciated addict, most people who overuse alcohol and drugs become adept at disguising their behavior. Shame, embarrassment, and fear of consequences are powerful motivators. And in many cases, the person who's drinking too much or using drugs doesn't want to recognize or admit that he's not in control of the situation.

Sadly, many times we don't find out until a tragedy, such as a drunk driving accident or an overdose, has occurred. And then we're left wondering why we didn't spot the signs of addiction earlier. Knowing these 20 secret signs of addiction can help you prevent that from happening.

1. Quantity controlOver time, a higher tolerance to alcohol or drugs leads people with addiction problems to increase the quantity and frequency of their substance of choice without showing signs of being out of control. You might notice that someone refills his or her glass more often than anyone else or is always the one to suggest opening another bottle of wine. Prescription drug users will start going through a prescription faster, complaining that they "ran out" or that "the doctor forgot to renew my prescription."

To spot drug dependence, notice if the person you're concerned about frequently seems to need an early refill, always with a different reason, says physician Gregory A. Smith, medical director of the Comprehensive Pain Relief Group in Redondo Beach, California. Excuses Smith says he's heard a thousand times: "The pills spilled into the sink and went down the drain." "My car got broken into, and they took my bag that had all my pills." "My brother's friend who has a drug problem stole my pills." "The pharmacy shorted me on my pills . . . there were supposed to be 120, but there were only 95 pills in the bottle when I got home and counted them."

2. Hide-and-seek around the houseQuick, check under the bathroom sink -- is there a bottle hiding behind the Ajax? How about in the laundry room behind the detergent, or in the garage? Finding a bottle or a six-pack tucked where it shouldn't be is one of the most common tip-offs that someone's drinking is getting out of hand. Similarly, pills and powders may turn up in glove compartments, the inside pockets of purses, jewelry boxes, or the toolbox.Over time, alcoholics and addicts develop a network of hiding places to stash their drugs. You may notice that the person is oddly protective of certain rooms or areas of the house or garage, insisting that they be kept private, says physician John Massella, regional program director of Gateway Rehabilitation Center in Pittsburgh. There may even be a sense that the family member is "guarding" the alcohol, Massella says. Outbursts of temper may ensue if someone disturbs the private territory.

3. The disappearing actWhen it comes to drug addiction, items don't so much appear around the house as disappear, says Jacqueline E. Barnes, author of The Whirlpool -- Surviving a Loved One's Addiction. "You notice that checks are missing from your checkbook, sometimes taken from the middle of the checkbook rather than from the back of it," Barnes says. The need for money and the desperation of addiction make anything fair game. "Items like cameras and jewelry begin to disappear from your house; family heirlooms are taken to a pawn shop," Barnes says. "Sadly, addicts lose touch with guilt and remorse. They'll sell anything belonging to family and friends to get money to buy drugs."

4. A head start"Priming the pump" or drinking alone before going out with friends is a big red flag, experts say. "Alcoholics will often drink wine, beer, or liquor before meeting with friends so that it appears that they're drinking the same amount as everyone else -- when, in fact, they're way ahead," says Joseph Garbely, chief medical officer at Friends Hospital in Philadelphia. Why? Alcoholics want to appear to be just like their friends in public, but their tolerance is much higher, so they have to drink a lot more.

5. Tricks and manipulationsHiding an addiction leads to constant subterfuge. Alcoholics will often drink before and/or after a social event, then drink very little while other people are imbibing. Teenagers and young adults who are starting to use drugs may throw parents and teachers off the track by admitting to use of a lesser drug, like pot, when harder drugs are the real problem.

And all alcoholics and addicts make great use of the "divide and conquer" strategy, manipulating family members by telling one thing to one person, something else to another. This typically takes the form of half-confessions. "They may be honest with one family member about one thing and honest about another thing to someone else, but no one family member will know everything," says John Massella of Gateway. If it feels like your family's getting tangled up in lies and half-truths, it's time to pay attention.

6. The money magnetDrugs are expensive, and so is stopping at the bar four times a week. Impaired judgment also leads many people to get in financial hot water simply by not minding the store.

Just about any unusual money behavior can tip families off to drug or alcohol abuse, experts say. Bills may pile up unopened, or someone might suddenly start selling possessions on eBay when he or she has never done so before. The manic periods of elation from coke and speed can send people on buying sprees; alcohol can fuel gambling binges. Other tip-offs: Asking friends for loans or using a family member's credit card without asking.

7. The clear choiceVodka is a drink of choice for alcoholics for one reason only: It's clear and looks just like water when poured in a tumbler. Vodka can also be added to soft drinks and juice without changing the color or giving off a noticeable smell.

"A definite sign of abuse is when people put vodka in their thermos and mix it with their morning coffee," says Neil Capretto, medical director of Gateway Rehabilitation Center in Pittsburgh. If someone you love switches from a previous drink of choice to vodka, it's cause for alarm. Ditto if sipping from their cup of coffee or coke reveals that it's spiked. Pay attention to grocery receipts, too -- is vodka on the list?

8. Missing in actionThat birthday party that Dad didn't show up for, the high school graduation your sister swanned into halfway through -- these are the kinds of things people remember when they look back and wonder why they didn't recognize a loved one's addiction sooner. Becoming unreliable and secretive is a trademark of the alcoholic or addict. They start to forget appointments, miss important events, roll in late to work or school.

Maintaining and hiding an addiction takes time; you have to make your connection, pop by the bar on the way home, stop for coffee to sober up. Sneaking around the house is another tip-off, including slipping into the house to reach the bathroom (and the toothpaste and Visine) before talking to anyone. If every time you turn around, your loved one seems to be somewhere else, trust your instincts and start checking up.

9. A narrower worldAs addiction takes hold, it tends to block out other interests and activities that used to be important sources of pleasure and fulfillment. Loss of interest in friends, sports, social activities, and anything else that used to define someone can be a clue that something's not right.Sometimes the signs of addiction can be as subtle as a sense that the person isn't himself anymore. "You might notice someone finding an excuse not to go to family functions because they know they'll be under tremendous scrutiny from 'the village that raised them' -- the extended family," says Joseph Garbely of Friends Hospital in Philadelphia.

Another sign of isolation is changing their daily routine without a good reason; they may be redirecting their steps as they try to avoid friends, coworkers, and family.

10. Magic bottlesChecking the state of the liquor cabinet is a time-honored ritual for those who live with heavy drinkers. Harder to spot but even more telltale is the "magic bottle" -- the bottle that never seems to get empty. If the liquid levels in liquor bottles seem to rise and fall mysteriously, your only recourse is to taste. Watered-down liquor is a sure sign that the person you're worried about wishes to hide his liquor intake from you.

You might also suspect that bottles are being hidden. "Many people with alcohol abuse and alcoholism hide beer cans, wine bottles, etc., at the bottom of their recycling bins so their neighbors don't get suspicious about their problem," says Neil Capretto of Pittsburgh's Gateway Rehabilitation Center. If you hear the clink of bottles being moved around in the recycling bin or carried out to the car late at night, your secret addict may be doing a midnight drop-off.

11. Can I try the diet you're on?Crystal meth, cocaine, and other "uppers" stimulate energy to the point that people feel like they can go and go and go without eating. Many have no appetite at all. A natural side effect of this behavior pattern is, of course, rapid weight loss.

While this seems like an obvious sign of abuse, it's actually frequently missed because it's not considered something to worry about, experts say. "Weight loss is usually seen as a positive thing in our society, so it's often overlooked as a symptom of drug abuse," says Joseph Garbely of Friends Hospital in Philadelphia.

12. Squeaky cleanSure we all want to be hygienic. But overuse of certain products signals that someone's trying to hide something. Constant use of gum or breath mints? Someone might be trying to mask the smell of alcohol. The same goes for excessive use of mouthwash or hand gel (and constantly smelling like these products). Antistatic dryer sheets treated with a fragrance can be used to disguise the smell of smoke on clothes.

A bottle of eyedrops in the purse can be a tip-off that someone's trying to hide reddened eyes, especially if he or she seems to go through bottles remarkably quickly. And eyedrops first thing in the morning? Enough said.

13. The bathroom gameWhere do you find prescription drugs? In the bathroom. And if your own bathroom cabinets are empty of supplies, the obvious next choice is other people's bathroom cabinets. Someone who's abusing prescription drugs won't be able to resist the temptation to scrounge them in other people's houses, usually by making pretenses to visit the bathroom.

What you'll notice, if you pay attention, is overly frequent trips and taking a long time during bathroom visits. Hint: Listen for the sound of water running for an extended time to disguise the noise of cabinets and drawers opening and closing. Another telltale oddity: When visiting a home with more than one bathroom, a drug user will find excuses to use a different bathroom each time. "People abusing prescription drugs may even attend real estate open houses just so they can look in unsuspecting homeowners' medicine cabinets," says physician John Massella of Gateway.

14. Mood managementMany family members describe the emotional experience of living with an alcoholic or addict as being like a roller-coaster ride. "Hallmarks of any kind of addiction are unstable mood and unpredictable emotions and actions," says addiction specialist Clare Kavin, director of the Waismann Method of dependency treatment. Moods can go from numb and calm to extremely aggressive within minutes, often with no apparent explanation.

Someone smoking a lot of pot will be in "slow-down mode, with no ambition or energy," says Liliane Desjardins, an addiction specialist and co-founder of Pavillion International, a recovery treatment center in Texas. "They're playing it mellow, but what's really happening is that thinking and feeling are impaired, as is the ability to make rational choices or to follow up on decisions."

15. Sleeping sickness"Mommy's asleep on the couch and won't wake up," is how a young child of an alcoholic or addict typically describes the behavior she witnesses, and it's a pretty apt description. Alcohol and many common drugs are sedatives, or "downers," which means they make you feel more relaxed but also make you sleep, and sleep heavily. If you notice that someone you're concerned about falls asleep at inappropriate times or has a hard time waking up, pay attention.

Excessive sleepiness can also signal crashing out after a drug binge, experts warn. "After cocaine or meth binges, users become listless and very low on energy and will sleep for days," says Harold Urschel, author of Healing the Addicted Brain and medical director of Enterhealth, a recovery center in Dallas. One clue that this isn't just the flu or a need to "sleep in" is that, just as suddenly, the person wakes up with a ravenous appetite.

16. Pain that never endsPrescription drug addiction is one of the most common types of addiction today, and abusers learn a closetful of tricks to get hold of medications. Back pain is one of the most common symptoms used to get pain meds, doctors say, because it's nondescript and hard to prove, even with testing. It's also relatively easy to fake. If a young, healthy person claims to be suffering from chronic back pain and asks for narcotic pain medication, look closely.

Another tactic is going to more than one doctor and getting prescriptions for similar drugs or claiming that certain drugs don't work. "If someone tells their physician that they're allergic to NSAIDs (nonsteroidal anti-inflammatory drugs) such as Motrin, and they say that only narcotics work for pain, that's a red flag," says Joseph Garbely of Friends Hospital in Philadelphia. The reason? When a patient says this, a doctor is automatically limited and can only prescribe narcotic painkillers, Garbely says.

17. Sickness without causeWhen people are abusing alcohol or drugs, they just don't feel good much of the time, so frequent, vague illnesses can be a sign that something's up. Sickness can also be an excuse to duck out of work. Typically, you'll hear a lot of different explanations, all of them vague and hard to prove or disprove, says Gregory Smith of California's Comprehensive Pain Relief Group. Seafood poisoning, headache, diarrhea, constipation, and "my back went out" are all common -- and sometimes real, sometimes not.

In addition, low energy, fatigue, and depression that seem to come on suddenly without reason may not be caused by the drug itself but by withdrawal, says Smith. All of these symptoms are likely to be accompanied by irritability and even flashes of anger, especially if you question their authenticity or seriousness.

18. Paranoia and panic attacksAttacks of paranoia are a well-known occurrence to anyone who's smoked pot, but they're also a common side effect of many other drugs and alcohol. Panic attacks, too, can be caused by many drugs, particularly stimulants.

Sometimes these symptoms are temporary, but over time drug addicts' personalities can completely change. "Cocaine alters the brain and can cause a variety of psychological symptoms, including thoughts that 'everyone is out to get me' or 'the walls are closing in around me,'" says Harold Urschel of Dallas.Those abusing alcohol and drugs may develop social anxiety, feeling nervous and anxious in public situations and avoiding them whenever possible.

19. The storytellerWould it surprise you to know that someone who proclaims dramatically that he hasn't had a drink in two weeks is probably an alcoholic? It shouldn't; telling stories to yourself and others is a natural reaction for someone who can't admit he has a drinking problem.

Even more frustrating, he may not even know they're stories. Drugs and alcohol cause memory lapses and blackouts; he may honestly not remember what happened. It's hard to admit that, of course, so rather than confess to a blackout, he makes up a story about it.

The lies don't just involve family members -- they can extend to bosses, doctors, cops, anyone in the person's life. Prescription drug addicts often take a family member such as a child or an aging parent to the doctor and try to get a prescription that they really intend for themselves. "The person will say: 'Listen, my mother won't tell you, but she's in terrible pain and really needs painkillers," says Joseph Garbely of Friends Hospital in Philadelphia.

20. The blame gameThe craziness that overtakes families when a family member is abusing drugs and alcohol can feel like a contagious disease. The reason? The need to deny the addiction leads to an epidemic of blame.

"Addicts and alcoholics are known for blaming, guilt-tripping, and making others responsible for their misery," says Liliane Desjardins of the Pavillion International treatment center in Texas. Endless excuses for bad behavior become the norm, but no matter what happens, somehow it's always someone else's fault. That dented bumper? Well, why did you leave the car in the driveway where he didn't expect it to be?

The blame game ups the conflict level; a formerly peaceful family can begin to feel like a war zone. But the conflicts are always the fault of someone other than the alcoholic or addict.